Selective alkaloid extraction



July 31, 1962 J, l 3,046,997

SELECTIVE ALKALOID EXTRACTION Filed Sept. 27, 1960 BRINE RESERVOIR SOLVENT l4 4 I RESERVOIR LIQUID- LIQUID 2 Ex- TRACTOR EFFLUENT 3 FTRAP 0 BRINE -9 LEAF 8 FLOW PERCOLATOR METER TRAP 6 PUMP EXTRACT/0N TIME, hours 3,046,997 SELECTIVE ALKALOH) EXTRACTEGN John D. Hind, Richmond, Va., assignor to Philip Morris Incorporated, New York, N.Y., a corporation of Virginia Filed Sept. 27, 1960, Ser. No. 58,825 12 Claims. (Cl. 131143) .This invention relates to the removal of alkaloids from tobacco. More particularly, it relates to an efficient process for selective extraction of nicotine and other alkaloids from tobacco while not materially affecting the content or properties of waxes, aromatics, flavoring and other constituents of the tobacco.

It has long been known to remove nicotine and other alkaloids from tobacco by solvent extraction. One serious drawback of known processes has been the concurrent removal of other solvent-soluble constituents from the leaf, including the waxes, certain fiavorings and aromatic fractions. It has been proposed to remedy this disadvantage by recovering these desirable fractions from the solvent extract and endeavoring to reconstitute them in the tobacco by spraying, soaking, impregnating in a solvent vehicle and the like. These procedures have had limited usefulness, however, for once Waxes, esters, and other constituents are removed from the tobacco, it has been diflicult to replace them in such a way as to restore to the tobacco its prior character.

it is therefore an object of the present invention to provide a method for selective removal of alkaloids from tobacco. It is a further object to provide a process for efiiciently removing alkaloids from tobacco while leaving the other constituents of the tobacco substantially unaffected. An additional object is to provide an economical method for denicot-inizing tobacco. Other objects will in part be obvious and will in part appear hereinafter.

I have found that the foregoing objects are efficiently accomplished by the steps of organic solvent extraction of the tobacco, selective removal of the alkaloid fraction from the solvent and recycling the alkaloid-relieved solvent to the same or other tobacco. In this manner, the extracting medium rapidly becomes saturated with solvent-soluble non-alkaloid constituents such as waxes, flavorings, etc. and accordingly ceases to act as a solvent for these constituents.

I have further found that the alkaloid content of the extracting medium may be selectively reduced by contasting the medium, following extraction of the tobacco, with brine. While the alkaloid fraction of the solute is thereby largely removed, the waxes, fiavorings, and other constituents of the solute are not materially afieoted. It is particularly advantageous that removal of substantial amounts of desirable sugars from the tobacco, a problem inherent in prior processes, is obviated by the method of this invention. The recycled extracting medium continues to act as a solvent for nicotine, but, being saturated with the other fractions, does not remove or otherwise substantially aifect them.

Although pure nicotine is largely insoluble in brine, nicotine and other alkaloids occur in tobacco as salts, and these salts are readily soluble both in brine and in common organic solvents. Many other tobacco constituents are also soluble in water or in brine, and it is accordingly desirable to avoid contact between the tobacco and either of these media during the extraction. For this reason I prefer to select as the extracting medium a solvent which, during contact with the brine, will not pick up an amount of brine water sulficient to act as an effective solvent for the water-soluble fractions of the tobacco. A further advantage realized by selecting such a solvent is that substantial deposits of salt on the tobacco are thereby avoided.

3,545,007 Patented July 31, 1962 ing (i.e., solubility of tobacco fractions in a partially I aqueous medium) and on brine content of the product tobacco may of course vary. It is within the skill of the art to establish such limits of tolerance, and it is likewise Within the skill of the art to know or to determine by simple test which solvents 'will be satisfactory under prescribed conditions. In general I have found that it is preferable to choose a solvent which will dissolve no more than 0.1% salt from the brine. A preferred solvent is methylethyl ketone (MEK). Other solvents are satisfactory and also preferred which have no greater mutual solubility with the brine, than does MEK. A partial list of suitable solvents includes methylisobutyl ketone and higher ketones, methylene chloride, trichloroethylene, hexane, isobutyl alcohol and higher lower alkyl alcohols. t will be obvious to those skilled in the art from the criteria given which solvents are adapted to be used in the process of this invention. Since the solvent may be removed from the extracted tobacco by ordinary artknown thermal means, it may also be desirable that the solvent boil below 100 C.

The brine may comprise any of a number of inorganic salts, the most common being NaCl. Other suitable materials include KCl, Na SO K NaNO KNO MgCl MgSO CaOl etc. The pH of the brine solution is preferably at or below 7, suitably in the range 4.0 to 7.0, although a pH on either side of this range may in particular instances be found desirable. So far as nicotine distribution between brine and solvent is concerned, the pH may be quite low, e.g. 2.5, but the smoking flavor of some tobaccos may begin to become impaired if the pH of the brine is below about 4.0. A preferred range of brine pH is 5.0 to 6.5, and for this reason the salts of a Weak acid and strong base generally will not be used as the brine.

Conversely, however, the salts of strong acids and weak bases are quite suitable as the brine. The salts of strong acids and strong bases may likewisebe used, and the pH may, if desired, be reduced by addition of acid or an appropriate buffer salt. Suitable acids for this purpose illustratively include hydrochloric, sulfuric, citric, phosphoric, acetic, tartaric, and malic acids. Suitable buifers and butter systems are well known to the art and illustratively include acetic acid/sodium acetate, citric acid/sodium citrate, malic acid/potassium malate, tartaric acid/ sodium tartar-ate, phosphoric acid/ potassium phosphate.

In the practice of this invention, the solvent is percolated through the tobacco and the saturated extract con tacted with a brine solution. The latter step is conveniently carried out in a liquid-liquid extractor, although equivalent means such as mixing the extract and brine solution and permitting them to separate into phases may be employed.

The process may be more fullyexemplified by reference to the accompanying drawing, in which FIGURE 1 is a schematic flow diagram of a process according to this invention. Tobacco is placed in a leaf percolator 1, which is equipped with a solvent reservoir inlet 2, a recycle inlet 3 and an outlet 5. Initially, fresh solvent or solvent which is saturated with Waxes and other non-alkaloid tobacco constituents is admitted to the percolator 1 through inlet 2. After percolating through the tobacco, the alkaloid-laden solvent is withdrawn through outlet 5 and trap 6 by means of pump 7 and is directed to liquidliquid extractor 10. The rate of flow may be regulated by fiow meter 8, diverted extracting solvent passing by conduit 9 back to the leaf percolator 1, which it enters at inlet 4.

Brine is concurrently supplied from reservoir 11 to the liquid-liquid extractor 10, where it meets the extracting solvent in countercurrent flow, the efiiuent brine passing to barometric leg 12 (the arrangement of the liquid-liquid extractor shown is for solvent lighter than water or brine but this does not preclude the use of an extractor arranged to handle solvents heavier than water or brine). The brine-contacted extracting solvent passes from liquid-liquid extractor 19 through trap 13 and is recycled through inlet 3 to leaf percolator 1. A pump and flow meter analogous to those provided in the solvent leg may be furnished to control the flow of brine.

As illustrative of the manner in which this invention may be carried out, the following examples, which are not to be taken in a limiting sense, are presented. All parts are by weight, except as otherwise indicated.

Example 1 Three 150 gram lots of burley leaf are successively extracted using about 1800 ml. of brine-equilibrated MEK in each run. Tobacco from the first run is discarded, and as much MEK solution as possible is recovered each time and carried over to the succeeding run.-

. Flow rates of MEK solution and brine through the liquid-liquid extractor are held at 98ml./ min. and at about 7 ml./min., respectively. Analysis of the leaf from the second run indicates that about 77% of the alkaloids have been removed after a six-hour extraction. The third extraction is carried out in the presence of 1.9 grams of citric acid (at a pH of 4.7) yielding, after a six-hour run, leaf from which 83% of the alkaloids are removed.

Cigarettes made from the extracted tobacco are very mild in comparison with the controls, but apparently none of the characteristic burley flavor is lost.

Example 11 Three-quarters pound of .burley leaf (assay 3.167 alkaloids) is extracted in a large percolator. 1000 ml. of brine and 3950 ml. of MEK are re-circulated throughout the system and contacted in a liquid-liquid extractor. ThepH of the brine is not adjusted and ranges between about 5.7 and 6.5. The process is conducted to permit determining whether brine will continue to absorb nicotine efliciently after several passes. The following data are obtained:

1 Tobacco is percolated with solvent for one hour prior to starting the flow through the liquid-liquid extractor.

The foregoing data demonstrate the rapid build up of alkaloid in the brine and further show that the rate of extraction remains high and nearly constant when the brine is re-circulated. The substantially linear increase in alkaloid concentration in the brine as the process is carried out is indicated by FIGURE 2, which is based upon the data of this example.

Example 111 Three-quarters of a pound of burley leaf (assay 3.16% alkaloids) is percolated with three liters of brine-equilibrated isopropyl alcohol. The alcohol phase is continuously contacted with brine (which is not recycled) in the liquid-liquid extractor at rates respectively of 32 and 4.2 mL/min. Twenty samples of isopropanol input and brine efiiuent are taken during a 35-hour run. Alkaloid contents are reduced steadily from 1.8 and 2.1 mg./ml. to

4 0.4 and 0.5 mg./ml., respectively, during this time, with extraction coeflicient steady 'at 1310.1. of the leaf alkaloid is found in the brine efiiuent.

Example IV The procedure of Example III is repeated using a fresh sample of leaf and adjusting the pH of the brine to approximately 4.8 by adding 4.3 gramsof citric acid. After a 12.5 hour run, the alkaloid contents of the isopropanol and brine solutions are reduced from 1.9 and 2.5 mg./ml. to 0.7 and 1.0 mg./ml., respectively. The average extraction coefiicient is slightly higher (.151).

Comparison of Examples III and IV shows the increased efiicacy of the brine extraction obtained by acidification as reflected in the higher extraction coeificient. Where the process run for equal lengths of time an even more striking difference is observed.

The tobacco recovered from Examples III; and IV contains an amount of salt which is considered excessive. This situation may be avoided by using a solvent with which brine is less miscible.

Examples V and VI Two batches of tobacco are extracted with MEK against a saturated brine solution and against an unsaturated brine solution, respectively. In the latter case, the leaf tends to bleed as the process is carried out and fairly substantial amounts of water-soluble leaf components are lost. No bleeding occurs where a saturated brine solution is used.

Example VII The effect of pH upon distribution coefl'icients for'nicotine salts in solvent-brine solutions is measured. By distribution coefficient is meant the concentration of solute in brine divided by the concentration of solute in solvent phase.

In an isopropanol-NaCl system, the coeflicient increases from 0.15 to 5.5 after the pH is lowered by various acids to 2.0. In trial extractions employing such a system the measured distribution coefiicien't ranges from 1.2 to 1.5. Similar determinations in an MEK-brine trial extraction show a distribution coefficient of about 6.0.

It is a further advantage of my invention that valuable nicotine or other alkaloid salts may be readily and economically recovered from the brine. To accomplish this, the alkaloid-laden brine is made alkaline, suitably by addition of NaOH or other alkali. The degree of alkalinity is not critical, a suitable pH being about 9 or 10. The alkaline brine is then contacted with a second solvent, preferably the same species of solvent which is em ployed in the extraction process, by countercurrent flow, shaking or other suitable means. The alkaloid fractions are thus transferred to the solvent from which they may be recovered by distillation, precipitation or other well known means. The brine is then reacidified and recycled to the extracting apparatus.

Nicotine is a valuable and expensive article of com merce and the foregoing procedure is particularly desirable since it provides a relatively inexpensive and efficient way of providing nicotine of substantial purity, largely free of fats and waxes.

It will be observed that by minor modification the apparatus shown in FIG. 1 may readily be adapted to divert the alkaloid-enriched brine'to a second liquid-liquid extractor after, which the alkaloid-relieved brine maybe recycled to the extraction portion of the apparatus illustrated in the drawing. Provision may advantageously be made to a-lkalize the brine prior to reaching such second liquid-liquid extractor and to neutralize or acidify it before it returns to engage in countercurrent flow with the first solvent from the leaf percolator. In this manner a complete and self-contained process yielding vboth substantially alkaloid-free tobacco and valuable nicotine by product may be achieved.

Further, the process of this invention may be performed on tobacco of inferior character unsuitable or undesirable as an ingredient in smoking products to yield valuable nicotine and other alkaloids. in this event, as in all cases where the alkaloid-relieved tobacco is not to be used for smoking, deposits of salt on the tobacco, and liberation of solvent from the tobacco become considerations of lesser consequence. Solvents of limited mutual solubility with the brine or those more easily liberated from the tobacco are in such instance no longer necessarily preferred.

I claim:

1. A process for selective removal of alkaloid from tobacco which comprises the steps of extracting tobacco with organic solvent, contacting the resultant solvent extract with brine to remove alkaloid selectively from said extract, recycling the alkaloid-relieved solvent to tobacco, alkalizing the alkaloi i-enriched brine, contacting said alkaloid-enriched brine with a second organic solvent to remove alkaloid from said brine, and recovering alkaloid from the resultant alkaloid-enriched second solvent.

2. A process for selective removal of alkaloid from to bacco, which comprises the steps of extracting tobacco with organic solvent, contacting the resultant solvent extract with brine to remove alkaloid selectively from said extract, and recycling the alkaloid-relieved solvent to tobacco.

3. A process for selective removal of alkaloid from tobacco, which comprises the steps of extracting tobacco with an organic solvent, said solvent having a mutual solubility with brine no greater than has methyl ethyl ketone, contacting the resultant solvent extract with saturated aqueous brine, whereby alkaloid is removed selectively from said extract, and recycling the alkaloidrelieved solvent to tobacco.

4. The process of claim 3 in which the organic solvent is selected from the group consisting of methylethyl ketone, methylisobutyl ketone, methylene chloride, trichloroethylene, hexane, and isobutanol.

5. The process of claim 3 in which the organic solvent is methylethyl ketone and the saturated aqueous brine is a saturated aqueous solution of sodium chloride.

6. The process of claim 3 in which the pH of the brine is between about 4.0 and about 7.0.

7. The process of claim 3 in which the pH of the brine is between about 5.0 and about 6.5.

3. In a process for the selective removal of nicotine from tobacco which includes the step of organic solvent extraction of said tobacco, the improvement which comprises contacting the nicotine-laden solvent with saturated 5 aqueous brine, whereby alkaloid is selectively removed from said solvent, and recycling the nicotine-relieved solvent to tobacco.

9. A method for recovering alkaloid from tobacco, substantially free from fats and waxes naturally occurring in tobacco, which comprises the steps of extracting tobacco with organic solvent, contacting the resultant solvent extract with brine, thereafter alkalizing the brine, contacting the alkalized brine with a second organic solvent, and recovering alkaloid from the second solvent.

10. A method for recovering nicotine from tobacco, substantially free from fats and waxes naturally occurring in tobacco, which comprises the steps of extracting tobacco with organic solvent, contacting the resultant solvent extract with saturated aqueous brine, said brine having a pH below 7, thereafter alkalizing the brine, contacting the alkalized brine with a second organic solvent, and recovering nicotine from the second solvent.

11. The method of claim in which the organic solvent is selected from the group consisting of methylethyl ketone, methylisobutyl ketone, methylene chloride, trichloroethylene, hexane, and isobutanol.

12. The method of claim 10 in which the organic solvent is methylethyl ketone and the saturated aqueous brine is a saturated aqueous solution of sodium chloride.

References Cited inthe file of this patent UNITED STATES PATENTS 802,487 Wimmer Oct. 24, 1905 1,294,310 Sayre etal Feb. 11, 1919 2,525,785 Feinstein et al Oct. 17, 1950 2,805,667 Von Bethmann Sept. 10, 1957 FOREIGN PATENTS 225,351 Switzerland Apr. 16, 1943 OTHER REFERENCES Spath et al.: Berichte Deutsche Chemische Gesellschaft, vol. 68, page 1667 (.1935). 

1. A PROCESS FOR SELECTIVE REMOVAL OF ALKALOID FROM TOBACCO WHICH COMPRISES THE STEPS OF EXTRACTING TOBACCO WITH ORGANIC SOLVENT, CONTACTING THE RESULTANT SOLVENT EXTRACT WITH BRINE TO REMOVE ALKALOID SELECTIVELY FROM SAID EXTRACT, RECYCLING THE ALKALOID-RELIEVED SOLVENT TO TOBACCO ALKALIZING THE ALKALOI 1-ENRICHED BRINE, CONTACTING SAID ALKALOID-ENRICHED BRINE WITH A SECOND ORGANIC SOLVENT TO REMOVE THE SULTANT ALKALOID-ENRICHED SECOND SOLVENT. FROM THE RESULTANT ALKALOID-ENTRICHED SECOND SOLVENT. 